Critical limb ischemia (CLI) imposes a major public health burden, resulting in high rates of death and disability. Thus far no medical therapy has been shown to ameliorate CLI. The goal of this proposal is to develop innovative therapeutic approaches for CLI with the use of endothelial progenitor cell (EPC) based therapies augmented by novel biomaterials-based approaches. These studies will investigate 3 novel bioactive peptide amphiphiles (PA) in combination with direct EPC injections or alone for repair ischemic limb tissue. One of the novels, bioactive motifs developed in our lab includes motifs that foster cell adhesion through a domain containing Arg-Gly-Asp-Ser (RGDS) we will extend preliminary data generated in our labs indicating that RGDS-presenting PA nanostructures enhance EPC function and investigate certain mechanisms responsible for these effects in models of critical limb ischemia. Another approach that we have explored is provision of an angiogenic signal with a vascular endothelial growth factor (VEGF) mimetic epitope. We will extend our preliminary in vitro and in vivo studies to evaluate the effect of VEGF-mimetic PA to improve perfusion in ischemic limb tissue. Abundant prior data from our lab has established that the morphogen Shh is activated post-natally in response to ischemia and that exogenous Shh can affect ischemic tissue repair. We have recently developed a novel, inject able liquid crystalline PA that provides sustained, local release of Shh protein and will investigate the use of this material to treat models of critical limb ischemia.